1. Field of the Invention
The present invention relates to color monitors and video display processes generally, and, particularly to, a video muting circuit which can prevent images, generated according to display data stored in a computer, from being displayed on the monitor for a predetermined period of time, so that data is prevented from being viewed by an unauthorized person should the user of the computer leave the computer unattended while the data is being transmitted to the display screen.
2. Discussion of Related Art
Generally, a computer stores data which can be provided to other computer using a communication system such as a local area network (LAN) or an internet service. The data stored in the computer can be viewed by printing the data on a print medium or by displaying the data on a screen of a computer monitor.
Generally, data to be displayed is provided to a video amplifier as either monochrome input signals or color (RGB) input signals and amplified to a predetermined voltage level and the inversely amplified to a voltage level suitable for driving a cathode ray tube (CRT). In some models, the amplifier stages provide brightness and contrast control functions besides the amplifying function. The contrast control function allows the user to control the gain of the video signal, and the sharpness of the images. In order to realize the video signal on the screen of the monitor, the output of an image output circuit should maintain the output voltage swing sufficient to drive a cathode of the CRT. The video amplifying output voltage via the second video amplifier is affected by the pospo type used in the cathode ray tube, transmissivity of the monitor screen glass, and brightness setup. In case of the color monitor, one contrast controller simultaneously varies the entire contrast levels of three electron guns. The brightness controller simultaneously varies all brightness levels of the three electron guns to thereby control the brightness of the screen. With such a circuit, a user could manually control the brightness and contrast to mute the video signal by preventing the display of data on the screen during his/her absence. I have noticed that when the user is away from the monitor, the data can be redisplayed on the monitor by an unauthorized person by their manually controlling brightness and contrast. In addition, I have found that power is wasted due to the unnecessary display of the data during the absence of the user.
Recent efforts in related arts such as U.S. Pat. No. 5,382,981 to Hitoshi Inaba, et al., entitled Video Muting Apparatus and U.S. Pat. No. 5,463,289 to Moon. J. Song entitled First Grid Muting Circuit mention muting operations involving contrast control for, respectively, preventing deterioration of a cathode electrode and raster distortion. Neither of these efforts however, provides microcomputer control for muting a video signal to prevent display of computer data during the absence of a user. Other efforts in the art such as those represented by U.S. Pat. No. 5,493,340 to Yae Y. Kim entitled Circuit For Displaying Screen Control Status Of A Monitor endeavored to provide a circuit for simply muting the RGB signals to enable on screen display status signals to be displayed instead the image represented by the RGB signals.